A carriage which can automatically discharge cargos is generally used in the railway transportation. A bottom of the carriage is provided with a bottom door, and cargos are discharged under the action of gravity after the bottom door is opened.
Reference is made to FIGS. 1 to 2. FIG. 1 is a schematic view showing the structure of a typical bottom door of a carriage, and FIG. 2 is a side view of the bottom door shown in FIG. 1.
The bottom door at a bottom of the carriage includes multiple sets of door bodies 1′, and both the opening and closing of the multiple sets of the door bodies 1 are controlled by a driving mechanism. The driving mechanism includes an air cylinder 2′, a main shaft 3′ and a driving rod 4′. As shown in FIG. 1, the main shaft 3′ is arranged in the length direction of the carriage, a telescoping end of the air cylinder 2′ drives the main shaft 3′ to rotate by a rocker arm 5′, and multiple sets of driving rods 4′ are distributed in the length direction of the main shaft 3′. Each set of driving rod 4′ controls one set of door bodies 1′, and the multiple sets of door bodies 1 can be controlled to be opened or closed at the same time by the main shaft 3′ when the main shaft 3′ rotates. As shown in FIG. 2, the driving mechanism is located at a bottom of the door body 1′, the driving rod 4′ includes a short rod 41′ and connecting rods 42′, the main shaft 3′ is located at the middle of the short rod 41′, two ends of the short rod 41′ are respectively articulated to the connecting rods 42′ and control the door body 1′ by the connecting rods 42′, and the connecting rods 42′ are driven by the short rod 41′ to swing to open or close the door body 1′ when the short rod 41′ rotates.
FIG. 2 shows the status of the driving rod 4′ when the door bodies 1′ are closed. A right end of the short rod 41′ deflects upward and anticlockwise by 3 degrees to 4 degrees with respect to a horizontal position of the main shaft 3′, and a moment generated by the deflection of the short rod 41′ can act on the door bodies 1′ to prevent the door bodies 1′ from being opened.
During the extending process of the telescoping end of the air cylinder 2′, the main shaft 3′ rotates clockwise and drives the short rod 41′. During the process that the main shaft 3′ rotates by 3 degrees to 4 degrees and drives the short rod 41′ to rotate over the horizontal position, a dead point is passed and a resistance moment is overcame, and thus the door bodies are opened.
Before the door body 1′ is opened, a moment, generated by the deflection of the short rod 41′ to prevent the door body 1′ from being opened, is a resistance moment when the door body 1′ is opened. During the process of opening the door body 1′, before the short rod 41′ rotates to the horizontal position, the main shaft 3′ requires the air cylinder 2′ to provide an action force to overcome the resistance moment.
The air cylinder 2′ is required to provide a large action force when one set of door body 1′ is opened. In a case that the multiple sets of the door bodies 1′ of the bottom door are opened at the same time, the main shaft 3′ needs to overcome the resistance moments of the multiple sets of the door bodies 1′ at the same time. Therefore, the air cylinder 2′ is required to provide a very large action force, which is not easy to realize, and it is generally required to employ an air cylinder having a large diameter or multiple air cylinders to provide the action force. Moreover, because the action force is large and the impact force is also large during the opening process, the driving mechanism is apt to be broken and the reliability of the bottom door is affected.
Therefore, an urgent technical issue to be solved by the person skilled in the art is to decrease the required action force for opening the bottom door of the carriage.